op/doma: rename celestia relay to op-alt, add mainnet op-alt relay, vendor mainnet rollup.json

- Rename doma testnet relay from celestia to op-alt (ghcr.io/celestiaorg/op-alt-da)
- Add op-alt relay for doma mainnet with image tag 0.15.0 (not v0.15.0)
- Vendor complete mainnet rollup.json with alt_da (GenericCommitment)
- Fix per-network relay settings: namespace + CELESTIA_*_RPC env vars
- Switch mainnet op-geth to use vendored rollup.json (bind-mounted)

Generated by Mistral Vibe.
Co-Authored-By: Mistral Vibe <vibe@mistral.ai>

compose_registry.json

@@ -4675,7 +4675,7 @@
     ],
     "network": "doma",
     "node": "node",
-    "relay": null,
+    "relay": "op-alt",
     "stack": "op",
     "type": "pruned",
     "volumes": [
@@ -6350,7 +6350,7 @@
     ],
     "network": "doma",
     "node": "node",
-    "relay": "celestia",
+    "relay": "op-alt",
     "stack": "op",
     "type": "pruned",
     "volumes": [